I could infect you could infect he could infect we could infect you could infect they could infect
V-ing form
I could be infecting you could be infecting he could be infecting we could be infecting you could be infecting they could be infecting
Perfect
I could have infected you could have infected he could have infected we could have infected you could have infected they could have infected
V-ing perfect
I could have been infecting you could have been infecting he could have been infecting we could have been infecting you could have been infecting they could have been infecting
Negation
Simple form
I couldn't infect you couldn't infect he couldn't infect we couldn't infect you couldn't infect they couldn't infect
V-ing form
I couldn't be infecting you couldn't be infecting he couldn't be infecting we couldn't be infecting you couldn't be infecting they couldn't be infecting
Perfect
I couldn't have infected you couldn't have infected he couldn't have infected we couldn't have infected you couldn't have infected they couldn't have infected
V-ing perfect
I couldn't have been infecting you couldn't have been infecting he couldn't have been infecting we couldn't have been infecting you couldn't have been infecting they couldn't have been infecting
Interrogative form
Simple form
could I infect? could you infect? could he infect? could we infect? could you infect? could they infect?
V-ing form
could I be infecting? could you be infecting? could he be infecting? could we be infecting? could you be infecting? could they be infecting?
Perfect
could I have infected? could you have infected? could he have infected? could we have infected? could you have infected? could they have infected?
V-ing perfect
could I have been infecting? could you have been infecting? could he have been infecting? could we have been infecting? could you have been infecting? could they have been infecting?
Interro-negative form
Simple form
couldn't I infect? couldn't you infect? couldn't he infect? couldn't we infect? couldn't you infect? couldn't they infect?
V-ing form
couldn't I be infecting? couldn't you be infecting? couldn't he be infecting? couldn't we be infecting? couldn't you be infecting? couldn't they be infecting?
Perfect
couldn't I have infected? couldn't you have infected? couldn't he have infected? couldn't we have infected? couldn't you have infected? couldn't they have infected?
V-ing perfect
couldn't I have been infecting? couldn't you have been infecting? couldn't he have been infecting? couldn't we have been infecting? couldn't you have been infecting? couldn't they have been infecting?